What is Resonance? Simple Explanation

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Resonance. Simple Explanation.

  •  What is resonance? What does it have to do with vibrations and energy?
  •  And what does “We resonate together” or “We are on the same wavelength” mean?
  •  And what does this have to do with quantum physics and music?

Resonance Frequency

Bob: Hi Alice, what is resonance?

Alice: Resonance occurs in oscillating or vibrating systems. Take a swing, for example. If you push a swing once, it starts to swing, right?

Bob: Yeah, sure.

Alice: Okay, now you want the swing to swing higher and higher. In other words, you want to increase its amplitude. What do you do?

Bob: I keep pushing it.

Alice: Right, but how?

Bob: I have to push at exactly the right moment. If I push at the wrong moment, I actually slow it down.

Alice: Exactly. That’s resonance. If you give the swing a short push, it will swing at a certain frequency. That’s its so-called eigenfrequency (or natural frequency).

Bob: What does frequency mean again?

Alice: The frequency tells you how many times the swing oscillates back and forth per second. Say it swings once per second. Then its frequency is 1Hz.

The frequency you push at is called the driving frequency. In order for your pushing energy to go into the swing, you have to push it at its eigenfrequency. This is why the eigenfrequency is called the resonance frequency.

Bob: I see. And if I push at the resonance frequency, then the swing will swing a little bit higher with each oscillation, so it gets a little more energy?

Alice: Right. Resonances occur all over the world. In musical instruments, resonance frequencies determine the sound you hear. With bridges and buildings, you want to prevent the wind from exciting their resonant frequencies, because otherwise they will fluctuate more and more and eventually be destroyed. This is also called a resonance disaster. Our entire radio/phone and internet technology uses resonances to transmit information efficiently. And resonances play a very special role in quantum physics.

Bob: That sounds exciting.

Resonance in Quantum Physics

Alice: It is. Atoms, electrons and even light are fundamentally waves. And these waves vibrate at certain frequencies. We can only see the atoms around us because the light that we see is in exactly the right frequency range.

Only when the frequencies match – they are also called “resonant” – can the light talk to the atoms and tell your eye where the atoms are. We only see things around us because the light is resonant with the atoms.

Bob: That’s awesome. Does that mean that air is invisible because the air atoms aren’t resonant with visible light?

Alice: Exactly. Of course, evolutionarily, our eye has evolved to see the exact frequency range of electromagnetic radiation that is resonant with solid atoms but not with air.

Bob: Makes sense. If it were the other way around, there would always be fog for us, and we would always be hitting our knees somewhere.

Alice: That’s true.

Resonance in Music

Bob: Yeah cool. How is that actually with music? When I play an A on a guitar, sometimes the A from my piano vibrates as well. Is that resonance too?

Alice: Yes! That’s a very good example. The note A has a frequency of 440Hz. That means the string vibrates 440 times per second.

These vibrations, amplified by the body of your guitar, also causes the air around it to vibrate. These air vibrations are then called sound waves. And these sound waves propagate through the room and then also shake all the piano strings.

But only the strings whose eigenfrequencies are an integer multiple of 440 Hz start to vibrate, because only there the timing of the energy provided by the sound waves fits perfectly. With all other notes, the timing does not fit and the energy doesn’t add up.

Bob: Because the mismatched timing immediately dampens the amplitude of the strings, right?

Alice: I’m impressed. You’re already using the right physics words.

Bob: One thing I don’t understand. You said that if you drive a piano string with its resonance frequency, it gets more and more energy. Shouldn’t the string vibrate more and more and the sound get should get louder and louder until it breaks?

Lifetimes of Vibrations

Alice: If there weren’t any energy losses, like friction for example, that would actually happen. But the string is attached somewhere and that’s where the string and the material it’s attached to gets warmer. So the vibration loses energy all the time. The maximum vibration amplitude is a result of a balance between energy input and energy loss.

The energy loss also determines how long it takes for the vibration to fade when you stop shaking it. This is called the lifetime of the vibration.

The lower this energy loss (the higher the lifetime), the stronger and longer the string can vibrate. And now comes something very interesting: the lifetime also determines how precisely you have to match the resonance frequency to make the string vibrate in the first place. The longer the lifetime, the more precisely you have to match the resonance frequency. This surprising correlation follows from wonderfully elegant mathematics called Fourier analysis. By measuring how a system reacts to different driving frequencies, you can calculate its vibration lifetime and energy loss.

Bob: That sounds super crazy, but I have to admit, that’s where it gets a bit too complicated for me. I’ll take a closer look at that when I run out of weed. But I have another question: What does it mean when someone says, “This person or that person resonates with me”? And does this have anything to do with the saying “We’re on the same wavelength”?

This resonantes with me

Alice: Actually, the wavelength of a wave is closely related to its frequency. They are related by the speed of propagation of the wave.

Bob: I don’t get it.

Alice: Imagine a runner. The speed of the runner is his step frequency times his step length, right?

Bob: Makes sense. The larger the steps and the faster he puts one foot in front of the other, the faster he is.

Alice: Right. And similarly, the speed of a wave is its wavelength times its frequency. In vacuum (or air), the speed of light is always the same. So if you know the frequency of your light, then you automatically know its wavelength. That’s why there are many pictures of the electromagnetic spectrum that show the wavelength instead of the frequency. It contains the same information.

Bob: Ah, I see. So the sentences “We are on the same wavelength” and “We resonate with each other” mean the same thing in terms of resonance?

Alice: Almost. Sometimes the propagation speeds of different waves are not the same. Nevertheless, these oscillations can excite each other.

In the case of resonance, their frequencies have to match and the wavelength is secondary for the time being. However, I am not sure whether any resonances are really excited during human interactions.

But in any case, neuronal circuits in the brain are triggered. This works with pattern recognition, as far as I understand it. However, I’m not quite sure how exactly neural circuitry is triggered.

Bob: Could any electronic resonances be involved? So that the electrical signals coming from our senses somehow resonate with the neural patterns in our brain?

Alice: Could be. But I don’t know. But your neural circuits are also triggered when you don’t like somebody at all. And then you say “We’re not on the same wavelength”.

This statement is then, at least from a scientific point of view, incorrect. But language is about communication, not scientific correctness. And as long as everybody knows what is meant by it, it doesn’t matter, I would say 😊

Law of Attraction

Bob: I agree! There’s a lot of talk about resonance in connection with the law of attraction. What you think and feel is drawn into your life by resonance. Both negative and positive. Does the term resonance make sense in this context?

Alice: Good question. If resonance plays a role in triggering neural patterns, the choice of words even makes sense. Because you are reprogramming your brain through emotional visualization. You create new neural patterns.

This makes your brain sensitive to situations that could bring what you want or what you don’t want into your life. If such a situation occurs, your brain lets you know by generating the corresponding emotion. Then you act differently than if these patterns were not present in your brain.

Bob: Ah, I see. That our thoughts don’t really send out waves that resonate with the universe and draw what you want into your life, we’ve already discussed here.

Alice: Right.

Bioresonance and the law of resonance

Bob: And what is a bioresonance? They talk a lot about the law of resonance.

Alice: Pseudo-scientific nonsense to sell a healing method called bioresonance therapy. Unfortunately, just like quantum physics, the term resonance is often misused in pseudoscience and esotericism to take money out of the pockets of unsuspecting people and orthodox medical sceptics.

Bob: Thank you, Alice. No one has ever explained resonance in such simple terms to me.


Conclusion: Resonance occurs when an oscillating system is driven with its resonance frequency. As a result, energy is supplied to the system at the right moments, such that it adds up. If the same system is driven at a different frequency, much less energy is transferred. The lower the energy loss of the oscillation, the stronger and longer it oscillates, but the more precisely you have to match the resonance frequency to make it vibrate at all.

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